fix: wrap main execution in try/catch to show errors instead of silent exit

scripts/install.ps1

@@ -1041,6 +1041,7 @@ function Invoke-Upgrade {
 # ─────────────────────────────────────────
 # 主流程
 # ─────────────────────────────────────────
+try {
     "" | Out-File $LOG_FILE
 
     # 检测是否是 iex / 管道执行（如 irm | iex）
@@ -1083,3 +1084,10 @@ if ($isIexExecution) {
     while ($true) {
         Main-Menu
     }
+} catch {
+    Write-Host ""
+    Write-Err "脚本错误: $_"
+    Write-Host "按 Enter 退出..."
+    $null = Read-Host
+    exit 1
+}